Devices are known in which an extended strip is located beneath the bottom one cf two sieves in a mold when the sieve guide is horizontal. Although such devices drain or suction well, they have the disadvantage that the draining or suctioning cannot be sufficiently regulated as desired without the use of complicated structures. As a result, too many fine particles from the sheet of material can be washed away. This disadvantage cannot be overcome without changing the shape of the liquid intake space, so that, if necessary, a mold with another shape must be used to minimize the pressure surges that disturb the drainage process.
Systems are known, for example as shown in European Patent Application No. EP-A-O 160, 615, in which short strips are arranged in intervals one after another in the flow direction to generate a small amount of pressure on the sieve and thus to achieve smaller but more frequent pressure surges. Other systems are known in which on both sides of the sieves there are groups of short strips, where the strips are displaced from one another in the flow direction of the sieves, so that one strip in a row on one side of the sieve is disposed opposite an empty space between two strips of the row on the other side of the sieve. These systems are, however, complicated to build as well as to handle. At high machine speeds there are particularly high pressure forces at work because the water films diverted to the strips separate the fine substances from the fabric.
One object of the invention is to create a simple device by which drainage is influenced and retention of the fine particles in the material layer is improved.